The [NiCl2(NH2(CH2)(12)CH3)(2)] complex supported on gamma-Al2O3 produces a catalyst which is considerably more active and sulfur-resistant for the hydrogenation of cyclohexene carried out in mild conditions than a conventional catalyst obtained from acid solutions of NiCl2 and even than the same complex unsupported. As determined by XPS, the active species is the complex itself, which is stable under the reaction conditions. The higher sulfur-resistance is attributed to electronic and geometrical effects. The catalyst system is considerably more resistant to poisoning with thiophene than with tetrahydrothiophene.